1. Field of the Invention
This invention relates to analog multipliers, and more particularly, to a CMOS (complementary metal-oxide semiconductor) current-mode four-quadrant analog multiplier, which is capable of generating an output current signal proportional in magnitude to the product of two input current signals.
2. Description of Related Art
An analog multiplier is a circuit that can accept two input signals in analog form and generate an output signal proportional in magnitude to the product of the two input signals. The input signals are typically voltages, in which case the analog multiplier is customarily referred to as a voltage-mode analog multiplier. An analog multiplier can be organized either as a two-quadrant or a four-quadrant circuit. A four-quadrant analog multiplier can multiply, divide, square, and extract the square root of the input signals when various external connections are made to the circuit.
Analog multipliers are widely used in analog circuits and systems, such as modulators, phase comparators, adaptive filters, AC-to-DC converters, sine/cosine synthesizers, to name just a few. Moreover, analog multipliers have found use in fuzzy logic controllers and artificial neural networks.
Most currently available analog multipliers, however, operate in voltage mode, which means that the inputs and output are all voltages, and therefore not suitable for use in current-mode systems. Moreover, conventional voltage-mode analog multipliers are sensitive to variations in temperature and process, and therefore are unsuitable for use in many VLSI (very large-scale integration) systems such as analog neural networks which require the use of a large number of multipliers.
There exists, therefore, a need for a current-mode analog multiplier which is insensitive to variations in temperature and process, allowing it to be suitable for use in various VLSI systems.